This invention relates to oil seals, particularly shaft seals wherein the primary sealing lip element is an annular wafer shaped article which completely surrounds the shaft to be sealed and is in light engagement therewith at its inner annulus, or seal lip as it is commonly referred to.
Typically the aforesaid primary sealing lip element is part of a metal cased assembly which is press fitted into a shaft housing bore. The entire metal cased seal assembly ordinarily comprises a cup shaped metal case having an outer cylindrical portion adapted for press fitted engagement with the bore of the housing and a radial flange extending radially inward from one end thereof, a seal element, a gasket between the seal element and radial flange of the cup shaped metal case, and a second metal case having a radial portion backing up the seal element axially inward of the first metal case radial flange. The two metal cases are crimped or otherwise tightly secured to one another in such manner that the seal element is likewise secured between the radial flanges of the two metal case member.
Typical of seals of this construction is that shown in copending patent application Ser. No. 426,373, filed Dec. 19, 1973, now U.S. Pat. No. 3,857,156, and assigned to the assignee of this invention.
The latest development in this type of seal includes making the primary sealing element of polytetrafluoroethylene or the like and incorporating therein unidirectional and bidirectional hydrodynamic oil feedback features which prevent oil from leaking past the lip portion of the sealing element. For example, a spiral groove or flute located on the air side of the sealing element in the area of the lip portion will prevent oil leakage in one direction of shaft rotation such as shown in the aforesaid pending patent application. Similarly, bidirectional hydrodynamic features can be provided with sealing element configurations such as shown in copending patent application Ser. No. 541,926, filed Jan. 17, 1975, now U.S. Pat. No. 3,984,113, and assigned to the assignee of this invention.
These seals work well for the intended purpose but assembly includes a great number of separate fabrication operations. Further, the design of such seals does not lend itself to adaptation for a dual lip seal and consequently their use is limited. Also, applicants desired a design which would reduce the raw material requirements so as to minimize as much as possible the current problems of availability and cost.